how to take away all the spaces and punctuation in a string? (python)

Question

def pre_process(t):
    """ (str) -> str
    returns a copy of the string with all punctuation removed, and all letters set to lowercase. The only characters in the output will be lowercase letters, numbers, and whitespace.

    """

Answer 1

Try the following code.

import re

string = 'This is an example sentence.'
string = re.sub(r'[^a-zA-Z\d]', string)

print(string)

You should get out Thisisanexamplesentance.

Answer 2

Just rebuild your string with only alpha-numeric characters:

''.join(_char for _char in _str.lower() if _char.isalnum())

Answer 3

This is the simplest function using regex I could put together to achieve your requirement.

import re
def pre_process(t):
    return re.sub(r'[^a-z\d ]','',str.lower())

It will return the input string in lower case, and omit any characters that are not letters, numbers or whitespace.